LAMICTAL 25MG TAB NEW

Indications

Approved Uses

Epilepsy (adjunctive and monotherapy for partial seizures, generalized tonic-clonic seizures, seizures associated with Lennox-Gastaut syndrome), maintenance treatment of bipolar I disorder to delay mood episodes

Off-Label Uses

Common off-label uses include neuropathic pain and trigeminal neuralgia; other off-label psychiatric uses (e.g., PTSD or borderline personality disorder) have limited/variable evidence and are not standard.

Dosage & Administration

Dosing by Condition

Adults-Epilepsy (adjunct): With valproate: 25 mg every other day x2 weeks, then 25 mg daily x2 weeks, then increase by 25-50 mg every 1-2 weeks; typical maintenance 100-200 mg/day. With enzyme inducers (carbamazepine/phenytoin/phenobarbital/primidone) and no valproate: 50 mg daily x2 weeks, then 100 mg/day in 2 divided doses x2 weeks, then increase by 100 mg every 1-2 weeks; typical maintenance 200-400 mg/day. Adults-Bipolar I (maintenance): No valproate/inducers: 25 mg daily x2 weeks, 50 mg daily x2 weeks, 100 mg daily x1 week, then 200 mg daily maintenance; with valproate: 25 mg every other day x2 weeks, 25 mg daily x2 weeks, 50 mg daily x1 week, then 100 mg daily maintenance; with enzyme inducers (no valproate): 50 mg daily x2 weeks, 100 mg/day x2 weeks, 200 mg/day x1 week, 300 mg/day x1 week, then 400 mg/day maintenance.

Initial Dose

25 mg once daily for 2 weeks (monotherapy, without valproate or enzyme inducers); 25 mg every other day for 2 weeks then 25 mg once daily for 2 weeks (with valproate); 50 mg once daily for 2 weeks (with enzyme-inducing AEDs without valproate

Maintenance Dose

Epilepsy (typical maintenance): 100-200 mg/day (monotherapy); 200-400 mg/day with enzyme-inducing AEDs (without valproate); 100-200 mg/day with valproate. Bipolar disorder (maintenance): 200 mg/day (100 mg/day with valproate; up to 400 mg/day with enzyme inducers).

Maximum Dose

700mg/day (with enzyme-inducing AEDs in epilepsy); 400mg/day (bipolar disorder with enzyme inducers)

Children's Dosage

Epilepsy (2-12 years, adjunct with valproate): Initial 0.15mg/kg/day for 2 weeks, then 0.3mg/kg/day for 2 weeks, maintenance 1-5mg/kg/day (max 200mg/day). Epilepsy (2-12 years, with enzyme inducers without valproate): Initial 0.6mg/kg/day for 2 weeks, then 1.2mg/kg/day for 2 weeks, maintenance 5-15mg/kg/day (max 400mg/day). Not approved for bipolar disorder under 18 years. Not recommended under 2 years

Dose Adjustment Notes

Slow titration is required to reduce serious rash risk; adjust dosing when used with valproate (lower doses) or enzyme inducers (higher doses); use reduced doses in hepatic impairment and consider lower maintenance/slow titration in significant renal impairment (especially end-stage renal disease).

How to Take

Oral use: swallow the tablet with water (with or without food) at the same time each day; do not crush/chew unless specifically instructed for a dispersible/chewable formulation (this SFDA product is a standard tablet).

Side Effects

Common Side Effects

Dizziness, headache, diplopia, blurred vision, nausea/vomiting, somnolence or insomnia, ataxia (lack of coordination), tremor, fatigue, and rash.

Side Effect Frequency

Very common (≥10%): dizziness, headache, diplopia/blurred vision, nausea, ataxia, somnolence; rash is common overall but can be ≥10% in some datasets. Common (1-10%): vomiting, insomnia, tremor, fatigue, back pain, diarrhea. Rare/very rare: serious cutaneous adverse reactions (SJS/TEN), DRESS, aseptic meningitis, suicidal ideation/behavior, hemophagocytic lymphohistiocytosis.

Safety & Warnings

Contraindications

Contraindication: hypersensitivity to lamotrigine or any component/excipient of the formulation.

Warnings & Precautions

Key warnings/precautions: strict slow titration to reduce serious rash risk (highest in first 2-8 weeks; increased with valproate or rapid escalation); discontinue for rash unless clearly non-drug-related; monitor for hypersensitivity/DRESS, HLH, aseptic meningitis, and suicidal thoughts/behavior; avoid abrupt withdrawal (taper ≥2 weeks when feasible); consider cardiac risk (conduction disorders/structural heart disease) and monitor/avoid in high-risk patients; estrogen-containing contraceptives can lower lamotrigine levels-dose adjustments/monitoring may be needed.

Age Restriction

Epilepsy: approved for patients ≥2 years (as adjunctive therapy for certain seizure types; monotherapy indications vary by jurisdiction). Bipolar I maintenance: approved for adults; not approved <18 years.

Driving Warning

May Cause Drowsiness

Drug Interactions

Drug Interactions

Major interactions: valproate increases lamotrigine concentrations (requires lower lamotrigine dosing); enzyme inducers (carbamazepine, phenytoin, phenobarbital, primidone, rifampin) decrease lamotrigine concentrations; estrogen-containing hormonal contraceptives decrease lamotrigine concentrations (and levels rise during pill-free week); some HIV protease inhibitor regimens (e.g., lopinavir/ritonavir, atazanavir/ritonavir) can decrease lamotrigine concentrations-monitor and adjust. Sertraline is not a consistent clinically significant interaction.

Interaction Severity

MAJOR: Valproate/divalproex (markedly increases lamotrigine concentrations and rash risk-requires much lower lamotrigine dosing/titration). MAJOR: Enzyme-inducing AEDs (carbamazepine, phenytoin, phenobarbital, primidone) and rifampin (reduce lamotrigine concentrations-often requires higher doses). MAJOR/MODERATE (clinically significant): Estrogen-containing hormonal contraceptives (can reduce lamotrigine levels ~50% and levels rise during pill-free week-dose adjustments/monitoring needed). MODERATE: Certain HIV protease inhibitor regimens (e.g., lopinavir/ritonavir, atazanavir/ritonavir) can lower lamotrigine exposure. MINOR: Antacids-no clinically meaningful interaction.

Food Interaction

No restriction.

Special Populations

Pregnancy

Category C (Risk cannot be ruled out

Breastfeeding

Caution

Children

Epilepsy (2-12 years, adjunct with valproate): Initial 0.15mg/kg/day for 2 weeks, then 0.3mg/kg/day for 2 weeks, maintenance 1-5mg/kg/day (max 200mg/day). Epilepsy (2-12 years, with enzyme inducers without valproate): Initial 0.6mg/kg/day for 2 weeks, then 1.2mg/kg/day for 2 weeks, maintenance 5-15mg/kg/day (max 400mg/day). Not approved for bipolar disorder under 18 years. Not recommended under 2 years

Elderly

Start at lower dose, titrate slowly. Mean effective doses are often lower (e.g., 50-150 mg/day) than in younger adults.

Kidney Impairment

No specific initial dose change is usually required, but use caution in significant renal impairment and consider reduced maintenance doses (including in end-stage renal disease) because metabolites may accumulate; titrate to clinical response/tolerability.

Liver Impairment

Mild hepatic impairment (Child-Pugh A): no adjustment needed. Moderate hepatic impairment (Child-Pugh B): reduce initial, escalation, and maintenance doses by approximately 50%. Severe hepatic impairment (Child-Pugh C): reduce initial, escalation, and maintenance doses by approximately 75%

Storage & Patient Advice

Missed Dose

Take the missed dose as soon as remembered unless it is close to the next dose; do not double doses. If lamotrigine has been missed for >5 half-lives (about 3-5 days, longer if on valproate), contact the prescriber because re-titration may be needed.

Stopping the Medicine

Do not stop abruptly; taper over at least 2 weeks when possible, but discontinue rapidly if serious safety concerns occur (e.g., rash, hypersensitivity).

Overdose

Overdose may cause ataxia, nystagmus, dizziness, seizures, decreased consciousness/coma, and cardiac conduction abnormalities (e.g., QRS widening); management is supportive with airway/ventilation as needed, activated charcoal if appropriate, and ECG/cardiac monitoring-seek emergency care immediately.

Patient Counseling

Take exactly as prescribed and do not stop abruptly; titrate slowly and do not change doses without advice. Seek urgent care for any rash (especially with fever, mouth sores, facial swelling, or swollen glands). Report mood changes or suicidal thoughts. Use caution with driving/alcohol until effects are known. Tell clinicians about all medicines-valproate, enzyme-inducing seizure medicines, and estrogen-containing contraceptives can require dose changes; if therapy is interrupted for several days, contact the prescriber as re-titration may be needed.

Monitoring Requirements

Monitor closely for rash and hypersensitivity (especially during the first 2-8 weeks and after dose increases), suicidal ideation/behavior and mood changes, and clinical seizure/mood control; consider baseline and periodic hepatic/renal assessment in at-risk patients; serum levels are not routine but may be useful in select situations (adherence, pregnancy, interactions, toxicity).

Pharmacology

Mechanism of Action

Inhibits voltage-sensitive sodium channels, stabilizing neuronal membranes and reducing presynaptic release of excitatory neurotransmitters (notably glutamate and aspartate).

Onset of Action

Clinical benefit is gradual due to mandatory titration: seizure control may improve over days to weeks as target doses are reached; bipolar maintenance/antidepressant benefit typically emerges over several weeks (sometimes longer).

Duration of Effect

Supports once- or twice-daily dosing; effective duration is driven by a long half-life (~25-33 hours in monotherapy, shorter with enzyme inducers and longer with valproate).

Half-Life

Approximately 25-33 hours in adults on lamotrigine monotherapy; ~14 hours with enzyme-inducing antiepileptics (e.g., carbamazepine, phenytoin, phenobarbital, primidone); ~48-70 hours with valproate co-therapy.

Bioavailability

Approximately 98% (high oral bioavailability).

Metabolism

Hepatic metabolism primarily via glucuronidation (mainly UGT1A4; also UGT2B7), with minimal CYP450 involvement.

Excretion

Primarily renal excretion of metabolites (mainly glucuronide conjugates), with a small fraction excreted unchanged in urine.

Protein Binding

Approximately 55% protein bound.

Product Information

Available Dosage Forms

Tablet, Chewable/dispersible tablet, Orally disintegrating tablet, Extended-release tablet.

Composition per Dose

Each tablet: 25mg lamotrigine

Generic Availability

Yes

OTC Alternatives

No OTC alternative

Psych Class

Mood Stabilizer

Controlled Substance

No

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